let array = [1, 2, 3, 4, 5, 6];
// 纯函数 输入相同 输出永远相同
console.log(array.slice(0, 3));
console.log(array.slice(0, 3));
console.log(array.slice(0, 3));

// 非纯函数
console.log(array.splice(0, 3));
console.log(array.splice(0, 3));
console.log(array.splice(0, 3));
